1. Field of the Invention
This invention relates to a process for treatment and disposal of sewage sludge.
2. Description of the Prior Art
Sewage sludge contains moisture holding organic matter and nutrients that can be beneficial when returned to nutrient and organic-poor but well drained agricultural land.
Sewage sludge in its originally derived form is unacceptable for land disposal for several reasons, including:
1. Raw sewage sludge contains all of the disease organisms common to man, as well as undesirable plant seeds. This material, in an untreated form, presents a health hazard and can create undesirable plant growths. PA1 2. Raw or undigested sewage sludge is highly putrescible and can be a nuisance, particularly from an odor standpoint, if it is allowed to decompose under uncontrolled conditions on the land. Decaying matter can also encourage undesirable insect propagation. PA1 3. If applied to agricultural land in an indiscriminate manner and at excessive application rates, the nitrogen in the sludge can contaminate ground water in the application area.
The known methods of processing sewage sludge involve thermal conditioning in such a manner as to improve the dewaterability of the sludge so that the solid and liquid phases are readily separated, as by sedimentation, filtration, centrifugation, etc., and the solid and liquid phases are then disposed of or subjected to further treatment separately (Teletzke et al. U.S. Pat. No. 3,256,179; Teletzke et al. U.S. Pat. No. 3,697,417; Erickson et al. U.S. Pat. No. 3,824,186).